Measuring transformers of this type are used to advantage in multi-functional measuring instruments such as for instance in electricity meters or wattmeters which measure two types of energy or performance simultaneously. They can also be used to measure a current in combination with another quantity or to measure a squared current and its time integral. In all instances the momentary value of an electric current is measured with the measuring transformer and is then multiplied by the momentary value of a voltage. Such a multiplication is preferably carried out with the help of a Hall element which, in its capacity as magnetic field sensor, serves to measure a magnetic induction produced by the current and thus to measure the current.
A measuring transformer used to measure the current flowing in an electric conductor is disclosed in "Hall Generators, Properties and Applications", by F. Kurth and H. J. Lippman, Springer Verlag, 1968, pages 10 to 11 and pages 267 to 275.
It is the object of the present invention to create a measuring transformer for measuring the current flowing in an electric conductor while avoiding the normally high expenditure incurred for several separate ferromagnetic cores, said measuring transformer being especially well suited for integration into a multi-functional measuring instrument or into other measuring instruments requiring at least two magnetic field sensors and evaluating at least one current value.